Inflatable packers have been used extensively in various well testing, treating and workover operations for many years. A typical inflatable packer has an elastomer sleeve that is mounted by end rings on a tubular body which is lowered into an open or cased well bore on a running string of jointed tubing, coiled tubing or wireline. When the packer is at the desired depth in the well, fluid pressure is applied to the interior of the sleeve via ports in the body to cause the sleeve to be expanded outward into sealing engagement with the well wall. Where an interval of the well is to be tested or treated which is off bottom, a so-called "straddle" packer arrangement is employed where two inflatable packers are run in tandem so that one bridges the well bore above the interval and the other one below same.
Since an inflatable packer is subjected to expansion forces as well as abrasion or cutting threes which can cause severe damage and possible malfunction thereof downhole, it has become common practice to armor the outside of the elastomer sleeve in various ways. One way is to use a plurality of longitudinally extending, overlapping slats that slide transversely relative to one another as the inner elastomer sleeve expands. Other structures include reverse-layed cables and woven composite cables or wires. All such constructions provide a protection for the sleeve against abrasion and cuts. Although the overlapping slats, cables or composite armor structures protect the elastomer sleeve or bladder of the inflatable packer, of their nature they are incapable of providing a seal against a well bore wall because of the external longitudinal passages formed by the manner in which they are arranged. Thus it is necessary to surround at least some portions of the armor members by an outer elastomer cover which provides sealing engagement with the well wall upon expansion of the inner elastomer sleeve. Such outer cover can be bonded to at least some of the armor members, or to portions thereof.
Although known straddle packer systems have had elastomer outer covers, such covers have been arranged in one of the following ways: (1) the entire lengths of each packer is completely covered; (2) centrally located covers with armor members exposed on either side thereof; (3) upper and lower covers on each packer with armor members exposed in the center regions thereof; (4) an upper elastomer cover on each packer with armor members exposed therebelow. However, after these packer systems are inflated, and during injection of fluid in the annular region between the set packers, the length of exposed armor members which are subjected to the pressure of injection fluids does not tend to anchor the packer because the walls of the packer from the diameter of the body having injection ports out to the cover/bore wall seal line tends to be pressure balanced. Thus the available length of the packer is not efficiently used.
An object of the present invention is to provide a new and improved straddle inflatable packer system which is more efficiently arranged.
Another object of the present invention is to provide a new and improved straddle inflatable packer system arranged such that substantially the full length on each packer tends to anchor in a well bore.
Still another object of the present invention is to provide a new and improved straddle inflatable packer arrangement having external elastomer covers positioned with respect to the isolated zone so that fluid leakage past the packers is minimized.